Pulp forming mold



Jan. 4, 1955 F. c. HARPER r 2,698,557

PULP FORMING HOLD Fildd Jun. 27, 1951 3 Ho E TOR INV N ML FRED c. HARPER H\S ATTO EY United States Patent Ofliee 2,698,557 Patented Jan. 4, 1955 PULP FORMING MOLD Fred C. Harper, Waterville, Maine, assignor to Keyes Fibre Company, Portland, Maine, a corporation of Maine Application June 27, 1951, Serial No. 233,833

2 Claims. (Cl. 92-54) This invention relates to mold constructions, more particularly to the type of molds used for forming pulp into a desired shape for the production of molded pulp articles.

Molds of the above type generally include a perforated body or base contoured to provide a fiber forming surface of the desired shape and this surface is lined with a relatively fine mesh screen. When the screen carrying surface is brought in contact with a slurry of fiber pulp and suction is applied to the mold perforations behind the screen, the liquid in which the pulp is suspended is sucked through the screen and the perforations while the suspended pulp fibers are trapped by the screen to produce a pulp layer having the desired shape. in many cases, however, particularly where the screen is of extended length or area, it is necessary to securely fix intermediate portions of the screen in place in order to assure the desired shaping of the pulp. In normal operation such intermediate portions have a tendency to adhere to the formed pulp layer and lift away from the body of the mold. The usual practice of applying air pressure through the mold to blow or lift the formed layer of pulp away from the mold, as when it is to be transferred to a different holder for subsequent treatment, greatly intensifies the lifting tendency. Unfortunately, intermediate screen anchoring devices used in the prior art cause local and sometimes unacceptable variations of the pulp layer. Furthermore, these prior devices have been awkward to apply and replace.

Among tne objects of the present invention is the provision of novel mold constructions which avoid the above and related disadvantages.

Further objects of the invention include the provision of novel anchoring elements which are used with the above type of molds to greatly reduce the effect of prior art anchoring devices on the pulp forming operations.

The above, as well as additional objects of the present invention will be more completely understood from the following description of several of its exemplifications, reference being made to the accompanying drawings wherein:

Fig. l is a sectional View of a screen-anchoring portion of a pulp forming mold of the present invention;

Fig. 2 is a perspective view of the anchoring device shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 showing a modified type of screen-anchoring construction embodying the present invention;

Fig. 4 is a fragmentary perspective view of a further form of anchoring device suitable for use in the construction of the invention; and

Fig. 5 is a perspective view of yet another anchoring device exemplifying the present invention.

According to the present invention, it has been discovered that a screen anchoring device can be used with pulp forming molds without producing any appreciable variations of the formed pulp layer, when the anchoring device is provided with one or more passageways for the transmission of the suction used to form the fiber layer. if in addition, the anchoring device including its passageway or passageways, is also covered with screening it will be difficult to even detect any formation variation.

Fig. 1 shows one highly practicable form of the present invention. A mold body which is conveniently formed of a thick block of metal, such as bronze, is

contoured to provide a desired external shaping surface 12 and is pierced by a multiplicity of passageways 14 extending from surface 12 to an internal surface 13. Over the shaped surface 12 is applied a screen 16 which covers passageways 14 and extends over the entire molding portion of surface 12. The margins of the screen are held in place in any suitable manner, this attachment forming no part of the present invention. Convenient arrangements for illustrating marginal supports are shown, by way of example, in Randall Patent No. 2,424,189 granted July 15, 1947, and Shepard Patent No. 2,238,853 granted April 15, 1941.

For holding an intermediate portion of the screen securely against surface 12, the mold body 10 can be pierced as indicated at 20 to receive an anchoring pin indicated generally at 30. In the form shown pin 30 is long enough to extend from mold surface 12 to and beyond the opposite surface 13. At one end the pin 30 has an enlarged head 32 with a flat top 33 and conically tapering lower surface 34. This head is completely covered with a bit of screening 36 that extends completely across the flat top and has its ends 38 tucked in under the tapering lower surface 34. In order to securely fix pin 30 in place, the mold surface 12 is countersunk as indicated at 4% to receive the enlarged head. If desired, the head 32 can be shaped to provide a design or surface configuration that can differ from the adjacent portions of screen 16 and thereby form a molded article incorporating this shape.

The pin 36 is provided at its opposite end with anchoring elements shown as a set of four resilient legs 42, each carrying a radially projecting locking tooth 44. These teeth project beyond and resiliently latch against the lower edge of passageway 29 to keep the pin securely in place. To mount the pin it is only necessary to push it in from the external surface 12 of the mold body. The legs which can be made slender enough to impart substantial resiliency to the locking teeth 44, flex to permit the teeth to be forced through the constricted portion of passageway 20. Upon emerging from the back end of this passageway, file teeth are snapped out into the latching position shown. Where the screen 16 extends across the passageway 20, it is preferably punched out to provide an opening for passage of the pin. However the pin can be shaped with its lower end pointed to automatically pierce the screen as it is pushed into place.

For withdrawal of the pin, a threaded socket 46 is shown as provided in the head of the pin shown in Fig. 1. The threading of a pulling tool into this socket enables very simple pin extraction, the teeth squeezing into passageway 20 as tension is applied to the pulling tool. If desired, the mold surface against which teeth 44 latch can be tapered as indicated at 5 This reduces the abrading action of the teeth and the latching surface on each other and permits many more latchings and unlatchings before dimensional tolerances are exceeded.

Socket 46 also forms part of a drain passageway that extends longitudinally completely through the pin from one end to the other. Through this passageway the slurry liquid in which pulp is suspended when sucked into the mold, freely drains so that the fiber formation over the head 32 is not much different from that at adjoining portions of the mold.

A feature of the present invention is the fact that with the cap screening 36, the passageway 46 acts to supply or distribute pulp forming suction to a sufficient area of screen 36 as to have the pulp form on this screening in a substantially identical manner as it forms on the adjoining screen 16. The joint between these two screens at the margins of pin 30 provides an additional amount of suction the effect of which extends the uniformity of pulp formation from the nearest passageway 14 to a small distance centrally from the margin of head 32. Without passageway 46 in the construction of Fig. l a pulp layer formed on the screened mold surface will show a very definite reduction in thickness over most of the head 32 of the pin.

The joint between screens 36 and 16 is shown somewhat exaggerated in the figure. In actual use each of these does no harm and where the pulp layer is subjected to the usual subsequent action ofpressing dies, any excessive thicknesswill be practically completely smoothed out. It should be noted that arlocal reduction in pulp thickness of the size corresponding to that produced by an unperforated pinprovides a marked weakness in the resulting article and cannot be appreciably leveled out by any amountof subsequent pressing.

In the construction ofFig. 3 arpin 136 generally similar to that of Fig. 1 is fittedinto mold body 110, but the pin is here provided with anchoring clips 144, 145 in the form of resilient wires suitably shaped and held in crossed slots 16!), 161 on the underside of head 132 as by swaging-or upsetting the'walls of the ,slots to pinch against the wires. The wires 144, 145 take the place of legs 42 in the pin of Fig. 2, .but the construction and operation can otherwise be quite similar.

As shown in Fig. 4, the anchoring pin 23% of the present invention can have one ormore drain passages 2.46 extending from the top of its head 232 only down to the tapering lower head surface 234. Inasmuch as the lower surface 234 and the adjacent portions of the mold are spaced apart by theinterposed screening ends, the construction of Fig. 4 provides an adequate drainage for the head. of the pin.

The pin construction of Fig. 5 has a plurality of radial V passageways 346 which, instead of opening on the lower surface of the pin head, join together to form a common passageway 347 extending through the shank of the pin. 'If desired, passageway 347 can be extended up through the top of the head, as indicated in the figure. This is particularly suited for anchoring pins having larger heads.

Slanted passageways as shown in Figs. 4 and 5 have the further advantage that they can be utilized as pin extracting sockets without requiring threaded engagement of an extracting tool, and by reason oftheir greater num-' ber can be made smaller so that less tearing of a covering screen is required for the penetration of an extracting tool. A bifurcated tool 270 with stifi arms shaped to fit into opposed passageways 246 by first being brought together, and then held apart as by a block, makes a convenient extractor for vthe pin of Fig. 4. A corresponding tool with oppositely acting arms is suitable for the pin of Fig. 5. In either case the thin arms of such extractors can be pushed right through the covering screen without preliminary punching or screen removal.

A convenient extracting technique for the threaded type of anchor is to first pierce the covering screen wlth a' tapered pin thatspreads the screen wires apart by a'distance corresponding to the size of the threaded passage Way. The pin can then be removed and an extractor inserted, or the extractor itself can be a threaded tool that tapers down below the thread to provide such a tapered Wire-spreading pin.

aged or fouled with pulp fibers or'other ingredients of A further feature of the present invention is that it provides .ascreen anchoring device which allows the screen to be readily applied, removed and replaced from the outer or screen covering face of the die without requiring any disassembly of the die itself. Accordingly, when a screen is to be replaced, as by reason of becoming damthe pulp slurry, the intermediate anchoring devices are readily removed. If the marginal screenanchorage is of the type in which these ends are clamped under a peripheral-externally applied die ring as in the above-identified Shepard patent for example, removal and replacement of the screen becomes a very simple matter even'though a plurality of intermediate anchorages are used.

As many apparently widely different embodiments of this invention maybe made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof, except as defined in the appended claims.

What is claimed is:

1. In a pulp-forming mold having an integral non-segmented shaped base structure with a forming surface including extended generally flat portions, a plurality of erforations extending through said base structure as pneumatic passageways for drainage of a slurry fluid therethrough, a screen fastened by its margin to cover the forming surface of said base structure to filter and form the fibers from a fibrous slurry, an anchoring aperture in at .least one of said generally flat portions, 'a corresponding aperture in the screen section covering the ansaid pin including. an enlarged-screen-covered head with References Citedin the-file-of this patent UNITED STATES PATENTS 889,064 Taylor May 26, 1908 1,161,125 Gill Nov; 23, 1915 1,169,693 Swedlund Jan. 25, 1 916 1,978,935 Douglas Oct. 30, 1934 2,118,800 Smith May 24, 1938 2,192,937 Shepard Mar. 12, 1940 2,359,201 Chaplin Sept. 26, 1944 2,601,815 De Reamer July 1, 1952 

